.bg-bubbles {
  padding: 0;
  margin: 0;
  position: absolute;
  // 使气泡背景充满整个屏幕；
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  // 如果元素内容超出给定的宽度和高度，overflow 属性可以确定是否显示滚动条等行为；
  overflow: hidden;

  li {
    border-radius: 50%;
    position: absolute;
    // bottom 的设置是为了营造出气泡从页面底部冒出的效果；
    bottom: -160px;
    // 默认的气泡大小；
    width: 40px;
    height: 40px;
    background-color: rgba(255, 255, 255, 0.5);
    list-style: none;
    // 使用自定义动画使气泡渐现、上升和翻滚；
    animation: square 15s infinite;
    transition-timing-function: linear;

    // 设置各气泡展示样式
    &:nth-child(1) {
      left: 10%;
    }

    &:nth-child(2) {
      left: 20%;
      width: 90px;
      height: 90px;
      animation-delay: 2s;
      animation-duration: 7s;
    }

    &:nth-child(3) {
      left: 25%;
      animation-delay: 4s;
    }

    &:nth-child(4) {
      left: 40%;
      width: 60px;
      height: 60px;
      animation-duration: 8s;
      background-color: rgba(255, 255, 255, 0.3);
    }

    &:nth-child(5) {
      left: 70%;
    }

    &:nth-child(6) {
      left: 80%;
      width: 120px;
      height: 120px;
      animation-delay: 3s;
      background-color: rgba(255, 255, 255, 0.2);
    }

    &:nth-child(7) {
      left: 32%;
      width: 160px;
      height: 160px;
      animation-delay: 2s;
    }

    &:nth-child(8) {
      left: 55%;
      width: 20px;
      height: 20px;
      animation-delay: 4s;
      animation-duration: 15s;
    }

    &:nth-child(9) {
      left: 25%;
      width: 10px;
      height: 10px;
      animation-delay: 2s;
      animation-duration: 10s;
      background-color: rgba(255, 255, 255, 0.3);
    }

    &:nth-child(10) {
      left: 85%;
      width: 160px;
      height: 160px;
      animation-delay: 5s;
    }
  }

  @keyframes square {
    0% {
      opacity: 0;
      transform: translateY(0px) rotate(0deg);
    }

    100% {
      opacity: 1;
      transform: translateY(-110vh) rotate(360deg);
    }
  }
}

.h1,
.h2,
.h3,
.h4,
.h5,
.h6,
h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: inherit;
  font-weight: 400;
  line-height: 1.1;
  color: inherit;
}

h3 {
  font-size: 24px;
  margin-bottom: 16px;
}